Coated carrier particles for electrostatographic development

ABSTRACT

Development is obtained in an electrostatographic imaging system with a developer mixture wherein the carrier particles are coated with a thin layer of a solid polyphenylene oxide resin or a blend of a polyphenylene oxide resin and a thermoplastic or thermosetting resin.

United States Patent 1191 Madrid et al. I

[ 11 Nov. 26, 1974 COATED CARRIER PARTICLES FOR ELECTROSTATOGRAPHICDEVELOPMENT [76] Inventors: Robert W. Madrid, 160 Jacobs Rd.,

Macedon; Robert J. Hagenbach,

235 Westmoreland Dr., Rochester, both of NY.

22 Filed: Apr. 9, 1 970 211 Appl. No.: 27,114

Related US. Application Data [63] Continuation-impart of Ser. No.585,739, Oct. 11,

1966, abandoned.

[52] US. Cl. 117/100 A, 117/17.5, 117/100 B, 117/100 M, 117/100 C,252/621 [51] Int. Cl. B05c 7/14, B44d 1/02, C030 25/00 [58] Field ofSearch 252/621; 117/100; 260/8075, 874, 47

[56] References Cited UNITED STATES PATENTS 2,857,290 10/1958 Bolton252/621 'P'rzmm Examiner-Ronald H. Smith Assistant Examiner.l. P.Brammer [57] ABSTRACT Development is obtained in an-electrostatographicimaging system with a developer mixture wherein the carrier particlesare coated with a thin layer of a solid polyphenylene oxide resin or ablend of a polyphenylene oxide resin and a thermoplastic orthermosetting resin.

3 Claims, N0 Drawings COATED CARRIER PARTICLES FOR ELECTROSTATOGRAPHICDEVELOPMENT This application is a continuation-in-part of copending U.S.application Ser. No. 585,739 filed Oct. 11, 1966, and now abandoned.

This invention relates in general to imaging systems and, moreparticularly to improved developing materials, their manufacture anduse.

The formation and development of images on the I surface ofphotoconductive materials by electrostatic means is well known. Thebasic xerographic process, as

taught by C. F. Carlson in U.S. Pat. No. 2,297,691, involves placing auniform electrostatic charge on a photoconductive insulating layer,exposing the layer to a light and shadow image to dissipate the chargeon the areas of the layer exposed to the light and developing theresulting latent electrostatic image by depositing on the image a finelydivided electroscopic material referred to in the art as toner. Thetoner will normally be attracted to those areas of the layer whichretain a charge, thereby forming a toner image corresponding to thelatent electrostatic image. This powder image may then be transferred toa support surface such as paper. The transferred image may subsequentlybe permanently affixed to the support surface as by heat. Instead oflatent image formation by uniformly charging the photoconductive layerand then exposing the layer to a light and shadow image, one may formthe latent image by directly charging the layer in image configuration.The powder image may be fixed to the photoconductive layer ifelimination of the powder image transfer step is desired. Other suitablemeans such as solvent or overcoating treatment may be substituted forthe foregoing heat fixing step.

Several methods are known for applying the electroscopic particles tothe latent electrostatic image to be developed. One development method,as disclosed by L. E. Walkup is U.S. Pat. No. 2,618,551 and E. N. Wisein U.S. Pat. No. 2,618,552, is known as cascade development. In thismethod, a developer material comprising relatively large carrierparticles having fine toner particles electrostatically coated thereonis conveyed to and rolled or cascaded across the electrostaticimage-bearing surface. The composition of the carrier particles is sochosen as to triboelectrically charge the toner particles to the desiredpolarity. As the mixture cascades or rolls across the image-bearingsurface, the toner particles are electrostatically deposited and securedto the charged portion of a latent image and are not deposited on theuncharged or background portion of the image. Most of the tonerparticlesaccidentally deposited in the background areas are removed by therolling carrier, due apparently, to thegreater electrostatic attractionbetween the toner and carrier than between the toner and the dischargebackground. The carrier and excess toner are then recycled. Thistechnique is extremely good forthe development of line copy images.

and the toner particles are drawn from the brush to the electrostaticimage by electrostatic attraction.

In most commercial processes, the cascade technique is carried out inautomatic machines. In these machines, small buckets on an endless beltconveyor scoop the developer material from a sump and convey it to apoint above an electrostatic image-bearing surface where the developermixture is allowed to fall and cascade or roll by gravity across theimage-bearing surface. The carrier beads along with any unused tonerparticles are then returned to the sump for recycling through thedeveloping system. Small quantities of toner are periodically added tothe developer mixture to compensate for the toner depleted during thedevelopment process. This process is repeated for each copy produced inthe machine and is ordinarily repeated many thousands of times duringthe usable life of the developer. It is apparent that in this process,as well as in other development techniques the developer mixture issubjected to a great deal of mechanical attrition which tends to degradeboth the toner and carrier particles. This degradation, of course,occurs primarily as a result of shear and impact forces due to thetumbling of the developer mixture on the xerographic plate and themovement of the bucket conveyor through the developer material in thesump. Deterioration or degradation of carrier particles is'characterizedby the separation of portions of or the entire carrier coating from thecarrier core. The separation may be in the form of chips, flakes orentire layers and is primarily caused by fragile, poorly adhereingcoating materials which fail upon impact and abrasive contact withmachine parts and other carrier particles. Carriers having coatingswhich tend to chip and otherwise separate from the carrier core must befrequently replaced thereby increasing expense and consuming time. Printdeletion and poor print qualityoccur when carrier particles havingdamaged coatings are notreplaced. Fines and grit formed from carriercoating disintegration tend to drift and form unwanted deposits oncritical machine parts. Many materials having high compressive andtensile strength either do not adhere well to the carrier core or do notpossess the desired triboelectric characteristics. The triboelectric andflow characteristics of many carriers are adversely effected whenrelative humidity is high. For example, the triboelectric values of somecarrier coatings fluctuate with changes in relative humidity and are notdesirable for employment in xerographic systems, particularly inautomatic machines which require carriers having stable predictabletriboelectric values. Another factor affecting the stability of carriertriboelectric properties is the susceptibility of carrier coatings totoner impaction. When the carrier particles are employed in automaticmachines and recycled through many cycles, the many collisions whichoccur between the carrier particles and other surfaces in the machinecause the toner particles carried on the surface of the carrierparticles to be welded or otherwise forced into carrier coatings. Thegradual'accumulation of permanently attached toner material to thesurface of the carrier particles causes a change in the triboelec tricvalue of the carrier particles and directly contributes to thedegradation of copy quality by eventual destruction of the tonercarrying capacity of the carrier. Further, many carrier coatingmaterials are difficult to apply to carrier cores because they tend toform thin filaments rather than smooth continuous coatings.

Since developer materials must flow freely to facilitate accuratemetering and even distribution during the development and developerrecycling phases of the elec trostatographic process, the presence offilaments and carrier having rough outer surfaces in developer materialsis unsuitable because the developer materials tend to cake, bridge, andagglomerate. Some carrier coating materials having acceptabletriboelectric and coating properties are unacceptable for employment ona commercial scale because they cannot be economically mass produced.For example, quality control of the triboelectric value of some resinblends is difficult to maintain because a slight deviation in componentpercentages causes the triboelectric value of the resulting product tochange drastically. Carrier coating materials having close tolerancetriboelectric values are particularly important in high speed automaticcopying machines. Thus, there is a continuing need for a better systemfor developing latent electrostatic images.

It is, therefore, an object of this invention to provide developingmaterials which overcome the above noted deficiencies.

It is another object of this invention to provide carrier coatingmaterials which tenaciously adhere to carrier cores.

It is a still further object of this invention to provide carriercoatings having stable triboelectric values.

It is yet another object of this invention to provide carrier coatingshaving high tensile and compressive strength.

It is a further object of this invention to provide coated carriershaving smooth outer surfaces.

It is still another object of this invention to provide toner impactionresistant carrier coatings.

It is a further object of this invention to provide carrier coatingmaterials having easily adjustable triboelectric values.

It is yet another object of this invention to provide carrier coatingswhich are more resistant to chipping and flaking.

It is another object of this invention to provide developers havingphysical and chemical properties superior to those of known developermaterials.

The above objects and others are accomplished, generally speaking, byproviding novel electrostatographic developer materials includingcarrier cores coated with a composition comprising a polyphenylene oxideresin. The resin component employed in the carrier coatings of thisinvention may comprise a polyphenylene oxide resin per se, or apolyphenylene oxide resin blended with one or more other resins. Thepolyphenylene oxide resin coating may be employed in any suitablethickness. Typically, the coating on the free flowing carrier particlesis at leastabout 1 micron in thickness. However, a coating having athickness of at least about 2.5 microns is preferred because the carriercoating will then possess sufficient thickness to resist abrasion andprevent any pinholes which would adversely affect the triboelectricproperties of the coated carrier particles. The maximum coatingthickness is generally determined by the amount of coating materialcapable of being coated on the core by any given coating technique whichproduces free flowing coated particles and which does not result inagglomeration. A practical maximum coating thickness for large sizecores is therefore about 20 microns. Within these limits, a coatingthickness of from about 3 to about 5 microns provides superior abrasionresistance and stable triboelectric properties. While not absolutelynecessary, excellent abrasion resistance and stable triboelectricproperties are generally achieved with a substantially smooth,continuous uniform coating of a polyphenylene oxide resin. However,superior abrasion resistance has been achieved with coatings which areneither uniform or continuous.

Any suitable linear polyphenylene oxide resin may be employed. Thesepolyphenylene oxide resins have the general formula:

wherein: R and R" are each selected from the group consisting of H andalkyl radicals having a total of up to 12 carbon atoms in R and R and nis a positive integer of at least about 25. Generally, the highmolecular weight film-forming polyphenylene oxide resins employed in thecarrier coatings of this invention are obtained by well knownpolymerization techniques such as the oxidative coupling of phenols.Oxidative coupling involves the reaction of oxygen with active hydrogensfrom different molecules to produce water and a dimer linked by anoxygen. In order to form polymers by the oxidative coupling technique, apolyphenylene oxide monomer must have at least two active hydrogens.Optimum impaction resistance is obtained with a polyphenylene oxideresin formed by the copper catalyzed oxidation of 2,6dimethylphenol. Theresulting polymer has methyl groups at R and R" in the general formulaset forth above. While a 2,6-xylenol monomer is preferred, any othersuitable phenol may be used to produce useful resin carrier coatings.Typical phenols include: phenol; Z-methylphenol; 2-propyl phenol; 2-isobutyl phenol; 2,6-diethyl phenol; 2,6-diisopropyl phenol; 2-ethyl-6-methyl phenol; 2,5-dimethyl phenol; 3,5-dimethyl phenol; and the like.

Any suitable resin may be blended with a polyphenylene oxide resin toform the carrier coating materials of this invention. These resins mayinclude natural resins, modified natural resins or synthetic resinsprepared by addition, condensation or any other technique provingsuitable. The polyphenylene oxide resin may be blended with other resinsin any suitable amount. Generally to maintain the properties of thepolyphenylene oxide resin as a coating it is present in the blend in atleast the major proportion. Typical natural and modified natural resinsinclude: gum copal, gum sandarac, rosin, fossil resins, zein, ethylcellulose, cellulose acetate, cellulose nitrate, gum nitrate, oxidizedrosin, pentaerythritol esters of rosin and the like. Typical syntheticresins include polymers, copolymers, terpolymers and other polymericstructures and modified polymeric structures including, for example,polyolefins such as polyethylene, polypropylene, chlorinatedpolyethylene, and chlorosulfonated polyethylene; polyvinyl andpolyvinylidine compounds such as polystyrene, polymethylstyrene,polymethyl methacrylate, polyacrylic acid, polyacrylonitrile, polyvinylacetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride,polyvinyl carbazole, polyvinyl ethers and polyvinyl ketones;fluorocarbons such as polytetrafluoroethylene,

polyvinylfluoride, polyvinylidenefluoride andpolychlorotrifluoroethylene; polyamides such as polycaproloctamo andpolyhexamethylene adipamide; polyesters such as polyethyleneterephthalate; polyurethanes; polysulfides; polycarbonates; epoxies suchas the condensation reaction product of epichlorohydrin with any one ofa bisphenol A, resorcinol, hydroquinone and ethylene glycol; phenolicresins such as phenol formaldehyde, phenol furfural and resorcinolformaldehyde;

amino aldehydes such as urea formaldehyde and mela-- mine formaldehyde;and mixtures thereof.

Excellent results are obtained with a carrier coating containing apolyphenylene oxide resin blended with the products of an additionpolymerization reaction between monomers or prepolymers of: l organosilanes, silanols or siloxanes having from 1 to 3 hydrolyzable groupsand an organic group attached directly to the silicon atom containingless than 8 carbon atoms and an unsaturated carbon to carbon linkagecapable of ad dition polymerization and (2) one or more silicon freetypes of unsaturated polymerizable organic compounds. These additionreaction products have a weight average molecular weight of at leastabout 5,000. Outstanding results are obtained with a carrier coatingcontaining a solid polymeric reaction product of monomers of prepolymersof:( l styrene and homologues thereof, (2) acrylate or methacrylateesters and (3) organo silanes, silanols or siloxanes having from 1 to 3hydrolyzable groups and an organic group attacheddirectly to a siliconatom containing less than 8 carbon atoms and an unsaturated carbon tocarbon linkage capable of addition polymerization. These organosiliconterpolymers are preferred additives because the resulting blendpossesses especially good triboelectric stability and synergisticresistance to toner impaction.

Typically. a solid copolymer addition reaction product may be obtainedfrom about 99.5 to about 50 percent, by weight, of an unsaturatedsilicon free organic compound and from about 0.5 to about 50 percent, byweight, of the above described polymerizable organomore than one organicgroup is attached to the silicon atom, only one of the organic groupsneed be unsaturated to enter into a polymerization reaction with otherunsaturated monomers. Hence, compounds such as dimethyl vinyl chlorosilanes are suitable. When more than one unsaturated organic groupattached to the silicon atom are present, these unsaturated groups neednot be identical. For example, vinyl allyl silicon chlorides andbromides may be employed. Partially condensed siloxanes in the liquidstate having reactive unsaturated organic groups attached to a siliconatom may be employed as a terpolymer reactant.

Suitable silicon free monomers or prepolymers with which the aboveorganosilicon compounds are particularly adapted to react to form thepolymeric organosilicon resin additives of this invention include theunsaturated compounds which normally form resinous polymers by additiontype polymerization. Monomers or prepolymers containing the unsaturationin a nonbenzoid group may be employed, such unsaturated monomers orprepolymers include those having ethylenic or acetylenic linkage. Thus,there are included olefins, diolefins, acetylenes and their derivatives,particularly derivatives having substituents such as halogen, alkyl,aryl, unsaturated alicyclic and other types of substitu ent groupsincluding, for example, nitrile or nitro groups. The unsaturated organicmonomers containing the unsaturation in a non-benzoid group also includeunsaturated hydrocarbons, aliphatic carbocyclic, and heterocycliccompounds including unsaturated alcohols, aldehydes, ketones, quinones,acids, acid anhydrides, esters, nitriles or nitro compounds. Typicalunsilicon composition. Typically the solid terpolymer comprises fromabout 5 to about 94.5 percent, by weight, of an unsaturated silicon freeorganic compound, from about 94.5 to about 5 percent, byweight, of anunsaturated silicon free organic compound-different from the firstmentioned silicon free compound and from about 0.5 to about percent, byweight, of one of the above described polymerizable organosiliconcompounds. Theunsaturated organic group attached to the silicon atomcontains the unsaturation in a non-benzoid group and is preferablyanunsaturated hydrocarbon group. Typical unsaturated organic groupsinclude: vinyl, chlorvinyl, divinyl, distyryl, allyl, diallyl, triallyl,allyl phenyl, dimethyl allyl and methacryloxypropyl groups. Typicalhydrolyzable groups include: ethoxy, methoxy, chloro, bromo, propoxy,acetoxy and amino groups. Examples of typical unsaturated organo silaneshaving hydrolyzable groups attached to a silicon atom include: vinyltriethosy silane, vinyl trimethoxy silane, vinyl-tris,(beta-methoxyethoxy), silane, gammamethacryloxypropyltrimethoxy silane,vinyl trichlorosilane, vinyl triacetoxy silane, divinyl dichloro silane,and dimethyl vinyl chloro silane. Suitable corresponding polymerizablehydrolysis products and the corresponding siloxanes may be substitutedfor the foregoing saturated monomers include: ethylene, propylene,butenes, isobutylene, pentenes, hexenes, methyl .methacrylate, methylacrylate, vinylchloride, vinylidene chloride, acrylonitrile, chlorovinylacetate, styrene, butadene, chloroprene, cyclopentadene, divinyl,benzene, cyclohexadiene, ethyl methacrylate, vinyl acetate, vinyltoluene, acetylene, phenylacetylene, ethylvinyl benzene, allyl chloride,allyl benzene, maleic anhydride, ethyl acrylate, diethylmaleate, butylacrylate, butyl methacrylate, isobutyl methacrylate, methacrylicanhydride, vinyl formate, and mixtures thereof.

Polymerization of the unsaturated organosilicon and unsaturated siliconfree unsaturated compounds are effected with any suitable free-radicalinitiator or catalyst capable of polymerizing the monomers orprepolymers. By a free-radical initiator or catalyst is meant a compoundwhich is capable of producing free-radicals under the polymerizationconditions employed, such as compounds having an --O-O or an --N=N-linkage. Examples of the more commonly employed free-,

radical initiators or catalysts include: alkyl peroxides, such astert-butyl hydroperoxide, and di-tert-butyl peroxide; acyl and aroylperoxides, such as dibenzoyl peroxide, perbenzoic acid, dilauroyperoxide, perlauric 0 polyphenylene oxide resin is therefore generallyat least present in the major amount in resin blends. However, anexception to this general rule has been found with combinations ofpolyphenylene oxide resins with the organosilicon terpolymers describedabove. As illustrated in the Examples below, optimum synergistic resultsare obtained when the polyphenylene oxide resinorganosilicon terpolymerresin ratio is from about 90:10 to about 25:75. The extremely highresistance to toner impaction is completely unexpected because thepolyphenylene oxide resin organosilicon terpolymer resin blend possesseshigher toner impaction resistance than either the polyphenylene oxideresin or the organosilicon terpolymer resin alone. No satisfactoryexplanation for this surprising result has been found.

When the carrier coatings of this invention contain thermosetting resinsblended with a polyphenylene oxide resin, the blending should beeffected while the thermosetting resin is in a monomeric or partiallypolymerized stage. Polymerization of the thermosetting monomer orpartially polymerized prepolymer may be completed in situ after theblend is applied to a carrier core. In situ polymerization may beeffectuated by any well known technique as by application of heat. If athermosetting resin prepolymer is employed, the prepolymer should be ina liquid or thermoplastic stage so that uniform blending of theprepolymer as a melt or in a solvent solution will be facilitated.

To achieve further variation in the properties of the final resinousproduct, well known additives such as plasticizers, reactive resins,dyes, pigments, wetting agents, and mixtures thereof may be mixed withthe resin coating of this invention. When an organosilicon polymer isblended with the polyphenylene oxide resin, hydrolysis of thehydrolyzable groups attached to the silicon atoms may be promoted bypre-treating the carrier core with any suitable hydrolyzing medium suchas .a dilute solution of acetic acid or by mixing the hydrolyzingmaterial with the organosilicon polymer prior to the coating operation.

Any suitable well known coated or uncoated carrier material may beemployed as the core of the carriers of this invention. Typical carriermaterials include sodium chloride, ammonium chloride, aluminum potassiumchloride, Rochelle salt, sodium nitrate, potassium chlorate, granularzircon, granular silicon, methyl methacrylate, glass, silicon dioxide,flintshot, iron, steel, ferrite, nickel, carborundum and mixturesthereof. Many of the foregoing and other typical carriers are describedby L. E. Walkup in U.S. Pat. No. 2,618,551; L. E. Walkup et al. in U.S.Pat. No. 2,638,416 and E. N. Wise in U.S. Pat. No. 2,618,552. Anultimate coated carrier particle diameter between about 40 microns toabout 600 microns is preferred because the carrier particles thenpossess sufficient density and inertia to avoid adherence to theelectrostatic latent images during the cascade development process.Adherence of the carrier beads to an electrostatographic drum isundesirable because of the fonnation of deep scratches on the drumsurface during the image transfer and drum cleaning steps, particularlywhen cleaning is accomplished by a web cleaner such as the web disclosedby W. P. Graff, Jr., et al. in U.S. Pat. No. 3,186,838.

The surprisingly better results obtained from the employment ofpolymeric carrier coating materials containing polyphenylene oxideresins and blends thereof may be due to many factors. For example, it ispostulated that the unusually low water absorption properties of thepolyphenylene oxide resins contribute to the stable triboel'ectricproperties thereof. Further, although it is not entirely clear, the highresistance of the carrier coatings to toner impaction may be at leastpartly due to the high tensile strength and heat resistance exhibited bypolyphenylene oxide resins, particularly blends of polyphenylene oxideresins with organosilicon terpolymers. The polyphenylene oxide coatingsof this invention adhere well to the carrier cores tested and are alsohighly resistant to chipping, and flaking.

The polyphenylene oxide resin coating compositions may be applied to acarrier core by any conventional method such as spraying, dipping,fluidized bed coating, brushing, and the like. The polyphenylene oxideresins or blends thereof may be applied as a powder, dispersion,solution, emulsion, or hot melt. When ap plied as a solution, anysuitable solvent may be employed. Solvents having relatively low boilingpoints are preferred because less energy and time is required to removethe solvent subsequent to application of the coating to the carriercore. Typical solvents include the halogenated aliphatics such aschloroform and 1,2- dichloro ethane; aromatic hydrocarbons such astoluene and o-chlorobenzene; and the like. Any suitable coatingthickness may be employed. However, the carrier coating should besufficiently thick to resist flaking and chipping. The quantity of resinto be applied to the carrier cores depends upon the density and thesurface area presented by the carrier cores. Typical coating weightsinclude from about 20 to about 1,000 grams of coating material perpounds of flintshot carrier cores haivng an average diameter of about600 microns.

Any suitable pigmented dyed electroscopic toner material may be employedwith the coated carrier of this invention. Typical toner materialsinclude: cumaroneindene resin, asphaltum, phenolformaldehyde resins,rosin-modified phenolformaldehyde resins, methacrylic resins,polystyrene resins, polypropylene resins, epoxy resins, polyethyleneresins and the like. Typical toner materials are disclosed by H. E.Copley in U.S. Pat. No. 2,659,670; R. B. Landrigan in U.S. Pat. No.2,753,308; M. A. Insalaco in U.S. Pat. No. 3,079,342 and C. F. Carlsonin U.S. Pat. Reissue No. 25,136.

The following examples further define, describe and compare methods ofpreparing the carrier materials of the present invention and ofutilizing them to develop electrostatic latent images. Parts andpercentages are by weight unless otherwise indicated.

EXAMPLE I A control sample containing 1 part colored toner particleshaving an average particle size of about 10 to about 12 microns andabout 99 parts coated carn'er particles available in the Xerox 813Developer sold by the Xerox Corporation, Rochester, New York is cascadedacross an electrostatic image-bearing surface. The resulting developedimage is transferred by electrostatic means to a sheet of paper whereonit is fused by heat. The residual powder is removed from theelectrostatic imaging surface by a cleaning web of the type disclosed byW. P. Graff, Jr., et al. in U.S. Pat. No. 3,186,838. After the copyingprocess is repeated 8,000 times, the developer mix is examined for thepresence of carrier coating chips and flakes. Numerous carrier chips andflakes are found in the developer mix.

EXAMPLE II A coating solution containing about 20 grams, by weight, ofpolyphenylene oxide resin, PPO Grade C- 1001 resin sold by the GeneralElectric Company, Pittsfield, Massachusetts, dissolved in about 100parts chloroform and 175 parts dichloro benzene is sprayed onto glassbeads having an average diameter of about 600 microns. About 20 grams ofpolyphenylene oxide resin is applied to about pounds of glass carriercores. After drying, the developing procedure of Example I is repeatedwith the foregoing coated carriers substituted for the Xerox 813 carrierparticles'An examination of the developer mix after test terminationreveals substantially no carrier coating chips or flakes.

EXAMPLE III A coating solution about grams, by weight, of a v resinblend comprising about 85 percent polyphenylene oxide resin and about 15percent of an organosilicon terpolymer resin consisting essentially ofthe addition polymerization reaction product between about 15 partssytrene, about 85 parts methyl methacrylate and about 5 parts of vinyltriethoxy silane dissolved in toluene is sprayed onto glass beads havingan average diameter of about 600 microns. About 10 grams .of resin blendis applied to about 5 pounds of glass carrier cores. After drying, thedeveloping procedure of Example I is repeated with the foregoing coatedcarrier substituted for the Xerox 813 carrier particles, an examinationof the developer mix after test termination reveals substantially nocarrier coating chips or flakes.

EXAMPLE IV A control sample containing one part pigmented resin tonerparticles having an average particle size of about 10 to about 12microns and about 99 parts coated carrier particles available in theXerox 813 Developer sold by the Xerox Corporation, Rochester,

. New York, is tumbled in a rotating cylindrical jar having a diameterof about 2 /2 inches and a surface speed of about 140 feet per minute.Most of the carrier coating separated in the form of flakes from thecarrier core EXAMPLE V Glass carrier cores having an average diameter ofabout 600 microns are spray coated with a coating solution comprisingabout 10 percent, by weight, of polyphenylene oxide resin derived fromthe oxidative coupling of ,2,6-dimethylphenol. About 20 grams of thepolyphenyleneoxide resin is applied to about 5 pounds of glass cores.After drying, the milling procedure of Example IV is repeated with theforegoing coated carrier particles substituted for the Xerox 813 carrierparticles. No chips or flakes are found. A slight amount of tonerimpaction is first observed after a milling time of about 144hours.

EXAMPLE VI The milling procedure described in Example V is continueduntil the cumulative milling time is about 240 hours. Upon terminationof the milling, no chips or flakes are found. Examination of the carriersurfaces reveals complete impaction.

EXAMPLE Vll Glass carrier cores having an average diameter of about 600microns are spray coated with a coating solution comprising about 10percent, by weight, of a resin blend comprising about 85 percentpolyphenylene oxide resin, PPO PR5311 resin sold by the General ElectricCo., and about 15 percent of an organosilicon terpolymer resinconsisting essentially of the addition polymerization reaction productbetween about 15 parts styrene, about 85 parts methyl methacrylate andabout 5 parts vinyl triethoxy silane. About 20 grams of the resin blendis applied to about 5 pounds of glass cores. After drying, the millingprocedure of Example IV is repeated with the foregoing coated carrierparticles substituted for the Xerox 813 carrier particles. A slightamount of toner impaction is first observed after a milling time ofabout 144 hours. No chips or flakes are found.

EXAMPLE VIII The milling procedure described in Example VII is continueduntil the cumulative milling time is about 240 hours. Upon terminationof the milling, no chips or flakes are found. Examination of the carriersurfaces reveals almost complete toner impaction.

EXAMPLE IX Glass carrier cores having an average diameter of about 600microns are spray coated with a coating solution comprising about 10percent, by weight, of a resin blend comprising about percentpolyphenylene oxide resin and about 25 percent of an organosiliconterpolymer resin consisting essentially of the addition polymerizationreaction product between about 50 parts styrene, about parts methylmethacrylate and about 5 parts vinyl triethoxy silane. About 20 grams ofthe resin blend is applied to about 5 pounds of glass cores. Afterdrying, the milling procedure of Example IV is repeated with theforegoing coated carrier particles substituted for the Xerox 813 carrierparticles. A slight amount of toner impaction is first observed after amilling time of about 192 hours. No chips or flakes are found.

EXAMPLE x- The milling procedure described in Example IX is continueduntil the cumulative milling time is about 240 hours. Upon terminationof the milling, no chips or flakes are found. Examination of the carriersurfaces reveals only slight toner impaction.

EXAMPLE x1- Glass carrier cores having an average diameter of about 600microns are spray coated with a coating solution comprising 10 percent,by'weight, of aresin blend comprising about 50 percent polyphenyleneoxide resin and about 50 percent of an organosilicon terpolymer resinconsisting essentially of the'addition polymerization reaction productbetween about 15 parts styrene, about 85 parts methyl metacrylateandabout 5 parts vinyl triethoxy silane. About 20 grams of the resin blendis applied to about 5 pounds of glass cores. After drying, the millingprocedure of Example IV is repeated with the foregoing coated carrierparticles substituted for the Xerox 813 carrier particles. A slightamount of toner impaction is first observed after a milling time ofabout 96 hours. No chips or flakes are found.

EXAMPLE XII The milling procedure described in Example XI is continueduntil the cumulative milling time is about 192 hours. Upon terminationof the milling, no chips or flakes are found. Examination of the carriersurfaces reveals almost complete toner impaction.

EXAMPLE XIII Glass carrier cores having an average diameter of about 600microns are spray coated with a coating solution comprising about 10percent, by weight, of an organosilicon terpolymer resin consistingessentially of the addition polymerization reaction product betweenabout 15 parts styrene, about 85 parts methyl methacrylate and aboutparts vinyl triethoxy silane. About 20 grams of the resin is applied toabout 5 pounds of glass cores. After drying, the milling procedure ofExample IV is repeated with the foregoing coated carrier particlessubstituted for the Xerox 813 carrier particles. A slight amount oftoner impaction is first ob served after a milling time of about 96hours. No chips or flakes are found.

EXAMPLE XIV The milling procedure described in Example XIII is continueduntil the cumulative milling time is about 192 hours. Upon terminationof the milling, no chips or flakes are found. Examination of the carriersurfaces reveals complete toner impaction.

EXAMPLE XV Steel carrier cores having an average diameter of about 250microns are spray coated with a coating solution comprising about 15percent, by weight, of a resin blend comprising about 90 percentpolyphenylene oxide resin NORYL resin sold by the General ElectricCompany, and about percent of an organosilicon terpolymer resinconsisting essentially of the addition polymerization reaction productbetween about 50 parts styrene, about 50 parts isobutyl methacrylate andabout 5 parts gamma-methacryloxypropyltrimethoxy silane. About 20 gramsof the resin blend is applied to about pounds of steel cores. Afterdrying, the mill ing procedure of Example IV is repeated with theforegoing coated carrier particles substituted for the Xerox 813 carrierparticles. A slight amount of toner impaction is first observed after amilling time of about 144 hours. No chips or flakes are found.

EXAMPLE XVI Flintshot carrier cores having an average diameter of about600 microns are spray coated with a coating solution comprising aboutpercent, by weight, of a resin blend comprising about 90 percentpolyphenylene oxide resin and about 10 percent of polycarbonate resin.About 35 grams of the resin blend is applied to about 5 pounds offlintshot cores. After drying, the milling procedure of Example IV isrepeated with the foregoing carrier particles substituted for the Xerox813 carrier particles. A slight amount of toner impaction is firstobserved after a milling time of about 240 hours. No chips or flakes arefound.

EXAMPLE XVII Iron carrier cores having an average diameter of about 500microns are spray coated with a coating solution comprising about 10percent, by weight, of a resin blend comprising about percentpolyphenylene oxide resin and about 25 percent of ethylenevinylacetatecopolymer resin. About 20 grams of the resin blend is applied to about10 pounds of iron cores. After drying, the milling procedure of ExampleIV is repeated with the foregoing coated carrier particles substitutedfor the Xerox 813 carrier particles. A slight amount of toner impactionis first observed after a milling time of about 144 hours. No chips orflakes are found.

Although specific materials and conditions were set forth in the aboveexemplary processes in making and using the developer materials of thisinvention, these are merely intended as illustrations of the presentinvention. Various other toners, carrier cores, substituents andprocesses such as those listed above may be substituted for those in theexamples with similar results.

Other modifications of the present invention will occur to those skilledin the art upon a reading of the present disclosure. These are intendedto be included within the scope of this invention.

We claim:

1. A carrier particle for electrostatographic developer mixturescomprising a particulate core surrounded by a thin outer layer, saidthin outer layer comprising from about 1 to about 20 microns inthickness of a blend of a polyphenylene oxide resin and a solidterpolymer of (1) from about 5 to about 94.5 percent, by weight of anunsaturated silicon free organic compound (2) from about 94.5 to about 5percent, by weight of an unsaturated silicon free organic compounddifferent from the compound of (1) and (3) from about 0.5 to about 50percent, by weight of a polymerizable organosilicon compound selectedfrom the group consisting of silanes, silanols, and siloxanes havingfrom one to three hydrolyzable groups and an organic group attacheddirectly to a silicon atom containing less than 8 carbon atoms and anunsaturated carbon to carbon linkage, the weight ratio of saidpolyphenylene oxide to said terpolymer being from about :10 to about25:75.

2. A carrier particle for electrostatographic developer mixturescomprising a particulate core surrounded by a thin outer layer, saidthin outer layer comprising from about 1 to about 20 microns inthickness of a blend of a polyphenylene oxide resin and a solidterpolymer of l from about 5 to about 94.5 percent, by weight, of astyrene composition, (2) from about 94.5 to about 5 percent, by weight,of a composition selected from the group consisting of acrylate andmethacrylate esters and (3) from about 0.5 to about 50 percent, byweight, of a polymerizable organosilicon composition selected from thegroup consisting of organosilanes, silanols, and siloxanes having fromone to three hydrolyzable groups and an organic group attached directlyto a silicon atom containing less than 8 carbon atoms and an unsaturatedcarbon to carbon linkage, the weight ratio of said polyphenylene oxideto said terpolymer being from about 90:10 to about 25:75.

3. A carrier particle for electrostatographic developer mixturescomprising a particulate core surrounded by a thin outer layer, saidthin outer layer comprising from about 1 to about 20 microns inthickness of a blend of a solid polyphenylene oxide resin'and a solidlinear addition terpolymer of (1) from about to about 94.5 percent, byweight, of a styrene composition, (2) from about 94.5 to about 5percent, by weight, of a methacrylate composition selected from thegroup consisting of methyl, ethyl, propyl, and butyl methacrylate and(3) from about 0.5 to about 50 percent, by

a diameter of from about 40 to about 600 microns.

fllhv n fl mobert W. Madrid and Robert J. Ha qenbach 1 and that saidLetters Patent are hereby UNITED STATES PATENT OFFICE EERTIFNATE oreoREcTroN Dated November 26, 1974 Patent No. 3,850, 676

It is certified that error appears in the above-identified patentcorrected asshown below:

Cover page, first column, after "{76} Inventors: Robert Madrid, 160Jacobs Rd. Macedon: Robert J" Hagenbach, 235 Westmoreland 'Dr.,Rochester, both of N.Y. insert --Assignee:

Xerox Corporation, Rochester, N.Y.--

Signed and sealed this 18th day of February 1975.

(SEAL) Attest:

RUTH C. MASON Attesting Officer C. MARSHALL DANN Cormuissioner ofPatents and Trademarks FORM PO-1050 (10-69) USCOMM-DC 603764 U.S.GOVERNMENT PRINHNG OFFICE: (969 0-86

1. A CARRIER PARTICLE FOR ELECTROSTATOGRAPHIC DEVELOPER MIXTURECOMPRISING A PARTICULATE CORE SURROUNDED BY A THIN OUTER LAYER, SAIDTHIN OUTER LAYER COMPRISING FROM ABOUT 1 TO ABOUT 20 MICRONS INTHICKNESS OF A BLEND OF A POLYPHENYLENE OXIDE RESIN AND A SOLIDTERPOLYMER OF (1) FROM ABOUT 5 TO ABOUT 94.5 PERCENT, BY WEIGHT OF ANUNSATURATED SILICON FREE ORGANIC COMPOUND (2) FROM ABOUT 94.5 TO ABOUT 5PERCENT, BY WEIGHT OF AN UNSTURATED SILICON FREE ORGANIC COMPOUNDDIFFERENT FROM THE COMPOUND OF (1) AND (3) FROM ABOUT 0.5 TO ABOUT 50PERCENT, BY WEIGHT OF A POLYMERIZABLE ORGANOSILICON COMPOUND SELECTEDFROM THE GROUP CONSISTING OF SILANES, SILANOLS, AND SILOXANES HAVINGFROM ONE TO THREE HYDROLYZABLE GROUPS AND AN ORGANIC GROUP ATTACHEDDIRECTLY TO A SILICON ATOM CONTAINING LESS THAN 8 CARBON ATOMS AND ANUNSATURATED CARBON TO CARBON LINKAGE, THE WEIGHT RATIO OF SAIDPOLYPHENYLENE OXIDE TO SAID TERPOLYMER BEING FROM ABOUT 90:10 TO ABOUT25:75
 2. A carrier particle for electrostatographic developer mixturescomprising a particulate core surrounded by a thin outer layer, saidthin outer layer comprising from about 1 to about 20 microns inthickness of a blend of a polyphenylene oxide resin and a solidterpolymer of (1) from about 5 to about 94.5 percent, by weight, of astyrene composition, (2) from about 94.5 to about 5 percent, by weight,of a composition selected from the group consisting of acrylate andmethacrylate esters and (3) from about 0.5 to about 50 percent, byweight, of a polymerizable organosilicon composition selected from thegroup consisting of organosilanes, silanols, and siloxanes having fromone to three hydrolyzable groups and an organic group attached directlyto a silicon atom containing less than 8 carbon atoms and an unsaturatedcarbon to carbon linkage, the weight ratio of said polyphenylene oxideto said terpolymer being from about 90:10 to about 25:75.
 3. A carrierparticle for electrostatographic developer mixtures comprising aparticulate core surrounded by a thin outer layer, said thin outer layercomprising from about 1 to about 20 microns in thickness of a blend of asolid polyphenylene oxide resin and a solid linear addition terpolymerof (1) from about 5 to about 94.5 percent, by weight, of a styrenecomposition, (2) from about 94.5 to about 5 percent, by weight, of amethacrylate composition selected from the group consisting of methyl,ethyl, propyl, and butyl methacrylate and (3) from about 0.5 to about 50percent, by weight, of a polymerizable organosilicon compositionselected from the group consisting of silanes, silanols and siloxaneshaving from 1 to 3 hydrolyzable groups and an organic group attacheddirectly to a silicon atom containing less than 6 carbon atoms and anunsaturated carbon to carbon linkage, the weight ratio of saidpolyphenylene oxide to said terpolymer being from about 90:10 to about25:75, said carrier particle having a diameter of from about 40 to about600 microns.